A variety of components has been proposed as an adsorbent for filtrating ingredients in smoke. As such components, in view of adsorbing an acidic component, formaldehyde, or others, components containing a basic component (such as an amine component) has been enough reported. For example, Japanese Patent Application Laid-Open Nos. 88078/1984 (JP-59-88078A) (Document 1), 151882/1984 (JP-59-151882A) (Document 2) and 54669/1985 (JP-60-54669A) (Document 3) disclose an adsorbent for cigarette filter, in which a polyethyleneimine, or an aliphatic amine having a low vapor pressure is impregnated to an active carbon. Japanese Patent Application Laid-Open Nos. 528105/2002 (JP-2002-528105A) (Document 4) and 528106/2002 (JP-2002-528106A)(Document 5) disclose a cigarette filter having 3-aminopropylsilyl covalently bonded to a related atomic group. Moreover, Japanese Patent Application Laid-Open No. 505618/2003 (JP-2003-505618A) (Document 6) discloses a filler containing an ammonium salt, and Japanese Patent Application Laid-Open No. 71388/1982 (JP-57-71388A)(Document 7) discloses addition of an amino acid for improving flavor of cigarette.
However, most of the basic components as described above, in particular, synthetic polymeric amines, often have a smell of a specific amine odor due to decomposition of the amines or remain of low molecular weight components. Moreover, the basic component itself or a volatile substance contained therein vaporizes and shows toxicity to the human body in many cases. Incidentally, the volatilization of the basic component can be inhibited by acidifying a solution thereof in the impregnation step. The basic component, however, has a potential for liberation for some reason, e.g., contact with other basic substances or hydrolysis. Further, although a component such as an amino acid is often crystallized and has a low volatile, enough adsorption effects in smoke cannot be expected because the amino acid has a low adsorption activity in such a crystal state. Thus, it has been considered that an adsorbent containing a conventional basic component has some effects on removal of the acidic substance or the aldehyde, however such an adsorbent has been impractical for the adsorbent for cigarette filter in terms of safety or effects thereof.
On the other hand, among such basic substances, a chitosan derivative such as a chitin or a chitosan does not crystallize or volatilize. Moreover, it is known that the chitosan derivative is harmless to the human body and has an antibacterial activity. For example, Japanese Patent Application Laid-Open No. 100713/1999 (JP-11-100713A) (Document 8) discloses a chitosan-containing cellulose acetate fiber which contains a chitosan and has an antibacterial rate of not lower than 26%. This document mentions that dispersion and inclusion of a chitosan in a spin dope, for example, by a manner such as a method of adding or mixing a chitosan-dispersed liquid to a dope for cellulose acetate, wherein the dispersion contains a chitosan pulverized to a size smaller than a predetermined size (a maximum particle size of not larger than 3 μm), or a method of adding or mixing a chitosan to the solvent directly and preparing the size of the chitosan by a certain dispersion condition.
Moreover, cigarette filters made of such a chitin or chitosan derivative have been also proposed. For example, Japanese Patent Application Laid-Open No. 142600/1978 (JP-53-142600A) (Document 9) discloses a cigarette filter containing a chitin or chitin derivative in a proportion of not less than 3 wt % relative to the cigarette filter. This document mentions that the chitin is poly-N-acetyl-D-glucosamine, and that a method for involving the chitin in the filter may include a method comprising directly blending a powder obtained from the chitin with a cigarette filter material, or a method comprising dissolving the chitin in a polar solvent such as acetic anhydride, dichloroacetic acid, methanesulfonic acid, or dimethylacetamide or dimethylformamide containing a chloride or a bromide of lithium, calcium or magnesium, then extruding the solution in a coagulant such as isopropyl ether to give a fiber or film, and blending the fiber or film with a cigarette filter material. Further, the document describes that, in the case of particularly blending the chitin and chitin derivative with an acetate filter, the chitin and chitin derivative imparts a distinctive light aroma and palatability to a cigarette due to a synergistic effect between an acetyl group in the derivative and an acetyl group in the acetate. To be concrete, the document mentions that the reducing (or removing) rate of tar is 34 to 41% and that of nicotine is 28 to 29% in Examples so that the characteristics are equivalent or more on conventional article.
Japanese Patent Application Laid-Open No. 168373/1985 (JP-60-168373A) (Document 10) discloses a cigarette filter comprising, as a material, a fiber consisting of a chitin or a derivative thereof (e.g., a chitosan obtained by deacetylation of part or all of acetylamino groups in the chitin, and a compound which is obtained by etherifying, esterifying, hydroxyethylifying or O-methylifying OH groups or CH2OH groups in a chitin). This document mentions that a production process for the fiber preferably includes a process comprising dissolving a chitin or a derivative thereof in a solvent to form a dope, and forming the dope into a fiber by a wet spinning process. The cigarette filter described in this document tends to adsorb tar or nicotine in use compared with a filter containing triacetylcellulose or a rayon as a material, and has an adsorption and adhesion performance one-and-a half times to twice or more as high as a conventional filter.
Japanese Patent Application Laid-Open No. 111679/1987 (JP-62-111679A) (Document 11) discloses a cigarette filter material containing a polysaccharide ion exchanger or a powdery polysaccharide (e.g., a cellulose, an agarose, an amylose, a chitin, and a chitosan) for removing a mutagenic compound in smoke during smoking. This document mentions that the polysaccharide ion exchanger or the powdery polysaccharide can be used as a filter of a cigarette body, or in the form dispersed or inserted in a space of an acetate filter.
Japanese Patent Application Laid-Open No. 31452/1995 (JP-7-31452A) (Document 12) discloses a cigarette filter containing a chitin or a chitosan in a proportion of 5 to 100% by weight. This document mentions that the chitin or chitosan may form, for example, a salt with a carboxylic acid (such as acetic acid, succinic acid, benzoic acid, phthalic acid, tartaric acid, malic acid or citric acid), an amino acid (such as glycine, glutamic acid or phenylalanine), an inorganic acid (such as a phosphoric acid or a boric acid), or a partial ester of an organic or inorganic polycarboxylic acid. Moreover, this document mentions that the chitin or chitosan may be used by impregnating a substrate comprising a powder or a fiber of, for example, silica, alumina, aluminosilicate, zirconia, activated carbon, or a cellulose (such as rayon, cotton or wood pulp), a starch, a protein (such as a gelatin or a casein), or a synthetic resin (such as cellulose acetate, a polyethylene, a polyester or a nylon) with the chitin or chitosan solution, and then drying the resulting matter. According to the filter described in this document, a harmful component such as nicotine, tar or an aldehyde in smoke can be effectively adsorbed and collected. Incidentally, as a concrete method using the chitin or chitosan solution, Example 5 has mentioned that a filter was formed by immersing 80 mg of an absorbent cotton in 1% aqueous solution of a chitin or chitosan (having a degree of deacetylation of 50%), vacuum drying the immersed cotton to give an absorbent cotton (100 mg) containing 20 mg of the chitin or chitosan, and filling the cotton in a paper pipe to form a filter chip, and the filter had a collecting rate of nicotine of 48%, that of tar of 45%, and that of acrolein of 72%.
Incidentally, it is conventionally considered that nicotine or tar is a main harmful component in smoke, and there is growing interest in delivery of nicotine or tar. Many countries obligate indication of nicotine and tar. However, it appears that nicotine itself is a taste component of a cigarette and directly takes part in contentment of smoking. Moreover, regarding tar, removal of a tar component in smoke at a relatively high level is not preferred because aroma and palatability are deteriorated. That is, indiscriminate reduction of low-volatile smoke components containing tar or nicotine brings about insufficient taste and feeling of unsatisfaction. On the other hand, an aldehyde, in particular formaldehyde, not only has a pungent odor but also effects on health adversely, and has attracted attention as one of allergens recently. Accordingly, it is consequently preferred to remove the aldehyde as much as possible.
It is therefore required to selectively remove an aldehyde component (particularly formaldehyde) in smoke while maintaining the amount of tar or nicotine in the smoke at a relatively high level.
However, although the cigarette filter containing the above-mentioned chitin or chitosan derivative have relatively safe on the human body, the filter highly removes not only the aldehyde such as formaldehyde but also a component such as nicotine or tar. As a result, the cigarette deteriorates taste and palatability (or aroma and palatability).
More specifically, in the case of directly using a particle or a fiber of the chitin, the chitosan derivative, or the like for a cigarette filter, the cigarette filter has non-selective adsorbality to formaldehyde, and highly adsorbs not only formaldehyde but also tar or nicotine as is the case with an activated carbon or others. As a result, the amount of tar or nicotine falls away, and the taste and palatability is not entirely satisfactory for smokers. Accordingly, smokers often unintentionally inhale smoke deeply or frequently during smoking.
Further, since the chitosan or the like is hard and fragile in its own, there is a possibility that, in a filter consisting of a fiber of the chitosan, the chitosan fiber dropped out from the filter is aspirated into the human body and causes injury to respiratory organs. Moreover, as described in the above-mentioned Document 12, even in the case of adding a chitosan particle to cellulose acetate filter which is used habitually as a cigarette filter, there is the possibility that the particle damages respiratory organs due to dropout.
Therefore, a cigarette filter enabling a small adsorption of tar or nicotine while maintaining selective adsorbability to formaldehyde has been required.
Document 1: Japanese Patent Application Laid-Open No. 88078/1984 (JP-59-88078A) (claims)
Document 2: Japanese Patent Application Laid-Open No. 151882/1984 (JP-59-151882A)(claims)
Document 3: Japanese Patent Application Laid-Open No. 54669/1985 (JP-60-54669A) (claims)
Document 4: Japanese Patent Application Laid-Open No. 528105/2002 (JP-2002-528105A) (claims)
Document 5: Japanese Patent Application Laid-Open No. 528106/2002 (JP-2002-528106A) (claims)
Document 6: Japanese Patent Application Laid-Open No. 505618/2003 (JP-2003-505618A) (claims)
Document 7: Japanese Patent Application Laid-Open No. 71388/1982 (JP-57-71388A) (claims)
Document 8: Japanese Patent Application Laid-Open No. 100713/1999 (JP-11-100713A) (claims, Paragraph number [0012])
Document 9: Japanese Patent Application Laid-Open No. 142600/1978 (JP-53-142600A) (claims; page 2, the upper left column, line 1 to the upper right column, line 2; and Examples)
Document 10: Japanese Patent Application Laid-Open No. 168373/1985 (JP-60-168373A) (claims; and page 1, the right column line 16 to page 2, the upper right column line 15)
Document 11: Japanese Patent Application Laid-Open No. 111679/1987 (JP-62-111679A) (claims; and page 2, the upper left column, lines 1 to 17)
Document 12: Japanese Patent Application Laid-Open No. 31452/1995 (JP-7-31452A) (claims; Paragraph numbers [0004], [0006]; and Examples)